U.S. patent number 4,158,875 [Application Number 05/908,612] was granted by the patent office on 1979-06-19 for air cooling equipment for electronic systems.
This patent grant is currently assigned to Nippon Electric Co., Ltd.. Invention is credited to Yohichi Matsuo, Tsuneaki Tajima.
United States Patent |
4,158,875 |
Tajima , et al. |
June 19, 1979 |
**Please see images for:
( Certificate of Correction ) ** |
Air cooling equipment for electronic systems
Abstract
An air cooling equipment for use in electronic systems of the
type having a plurality of printed circuit wiring boards with a
plurality of heat-generating electronic components mounted thereon
is disclosed. The air cooling equipment uses a double-walled duct
construction whereby air as a coolant is introduced in a direction
at high angles to the length of the heat-generating electronic
package.
Inventors: |
Tajima; Tsuneaki (Tokyo,
JP), Matsuo; Yohichi (Tokyo, JP) |
Assignee: |
Nippon Electric Co., Ltd.
(Tokyo, JP)
|
Family
ID: |
13147718 |
Appl.
No.: |
05/908,612 |
Filed: |
May 23, 1978 |
Foreign Application Priority Data
|
|
|
|
|
May 24, 1977 [JP] |
|
|
52/60627 |
|
Current U.S.
Class: |
361/695;
174/16.1; 361/690; 62/418 |
Current CPC
Class: |
H05K
7/20154 (20130101) |
Current International
Class: |
H05K
7/20 (20060101); H05K 007/20 () |
Field of
Search: |
;361/383-385 ;62/418
;174/15HP,16R,16HS ;165/80,105 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Tolin; Gerald P.
Attorney, Agent or Firm: Sughrue, Rothwell, Mion, Zinn and
Macpeak
Claims
What is claimed is:
1. Air cooling equipment having a plurality of printed circuit
wiring boards with a plurality of heat-generating electronic
components mounted thereon, said air cooling equipment
comprising:
a plurality of first covers of a "U" shape which cover said
components on said printed circuit wiring boards and are provided
in one-to-one correspondence to said printed circuit wiring
boards;
first intake ports and first exhaust ports of a plurality of first
air passages defined by said first covers and said boards, blowers
provided at selected ones of said ports;
a second cover having a second intake port adapted to supply air to
said first intake ports through a second air passage provided in
the same direction as the direction of air delivered as a coolant
in said first air passages, and a second exhaust port adapted to
discharge air exhausted from said first exhaust ports of said first
air passages in the same direction as that of air from the said
second intake port, said second cover defining a third air passage
in cooperation with said printed circuit wiring boards to cover
said boards therewith; and
a partition wall secured to said first covers and to said second
cover so as to separate air of said second intake port provided in
the second cover and said second exhaust port.
2. An air cooling equipment as claimed in claim 1, wherein said
partition wall is so inclined that the cross-sectional area of said
second intake port and said second exhaust port provided in the
second cover may be maximized.
3. An air cooling equipment as claimed in claim 1, further
comprising at least one thermally conductive member contacting an
electronic component mounted on one of said printed circuit wiring
boards and projecting through the corresponding one of said first
covers into said second air passage.
Description
BACKGROUND OF THE INVENTION
This invention relates to an air cooling equipment for use in
electronic systems such as communications systems and information
processing systems, and more particularly to an air cooling system
for electronic components mounted on printed circuit wiring boards
installed in those systems.
In general, active elements such as transistors mounted on the
printed circuit wiring board tend to generate heat proportional to
the dissipated electric power. The heat produced has an adverse
effect on characteristics of the active elements and, if too great,
can lead to the destruction of those active elements. For this
reason, a strict temperature restriction is imposed on these
electronic components to ensure reliability. This restriction is
easily met in circuits using only a few active elements; however,
an increase in the number of active elements is accompanied with
the increase of the electric power dissipation and the quantity of
heat produced which must be dissipated. This is typically
accomplished by means of a cooling equipment for effectively
cooling the electronic components so as to maintain the temperature
of the electronic components below their maximum operating
temperature.
One attempt for the practical use of such a cooling equipment is
disclosed in a liquid cooling system in Japanese Patent Application
Disclosure No. 8776/1977 (corresponding to U.S. patent application
of Edward A. Wilson et al, Ser. No. 592,578, now U.S. Pat. No.
4,072,188, filed Feb. 7, 1975, and assigned to HONEYWELL
INFORMATION SYSTEMS, INC.). However, a complicated mechanism for
liquid flow is unavoidable in such a system, which consequently
leads to a bulky system. Also, as the system becomes bulky,
defective parts tend to occur in the system. As a result, in the
event that a hole is found in a liquid passage, liquid leaks
therethrough with the result that the intended cooling function
cannot be achieved. Another attempt for that purpose is disclosed
in a gas (air) cooling system shown in FIG. 194(A) on page 327 of
Heat Transfer In Micro-Electronic Equipment (A Practical Guide) by
J. H. Seely and R. C. Chu, published by Marcel Dekker, Inc., New
York in 1972. This system supplies air as a coolant upwards from a
blower mounted at the lower end of a support so as to cool
electronic components provided on a plurality of component cards.
The temperature T of the heat-generating electronic components,
when such an air cooling system is used, is given as follows:
wherein Ta represents the temperature of a room with a system
provided with the electronic components, dTa represents a
temperature rise at the inlet of a duct relative to the room
temperature, dTb represents a temperature rise measured around
those electronic components as compared with the temperature at the
inlet of the duct, and dTc represents a temperature difference
attributable to the thermal resistance prevailing from ambient air
surrounding the electronic components to the components. In this
respect, dTa in the second term of the right-hand side of equation
(1) is negligible because the air at the room temperature is
directly used for the purpose of cooling. Accordingly, the
considerations in the design of a cooling system should be paid to
a decrease in dTb and dTc in the third and fourth terms of the same
side of equation (1), respectively. In this case, dTc is inversely
proportional to an air velocity, but if the air velocity exceeds a
given level, then the tendency of a decrease in dTc decreases
markedly. As a result, an important factor to be considered in
cooling the heat-generating electronic components is dTb. The
factor dTb is inversely proportional to the flow rate of air
supplied as the coolant and decreases with an increase in the flow
rate of the coolant air. Meanwhile, the air flow rate varies due to
the system resistance increasing in proportion to the length of air
passage, thus failing to provide air flow rate of more than a given
level. For this reason, in order to obtain the air flow rate
required for fully cooling the electronic components, a bulky air
blower is needed resulting in a high level of noise.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a
cooling equipment free from the above-mentioned shortcomings
experienced with the prior art systems by adopting a double-walled
duct construction and introducing air as a coolant in the direction
at a right angle to the length of the heat-generating electronic
package, thereby reducing the system resistance to the air flow
passing through a duct so as to increase the flow rate of the
coolant air, to thereby maintain the temperature of heat-generating
electronic components as low as possible as well as to provide
excellent adaptability of the cooling equipment.
The present equipment comprises a plurality of printed circuit
wiring boards with a plurality of heat-generating electronic
components mounted thereon; a plurality of first covers of a "U"
shape which cover said components on said boards and are provided
in one-to-one correspondence to said printed circuit wiring boards;
a plurality of blowers provided at least on one side at first
intake ports and first exhaust ports of a plurality of first air
passages defined by said first covers and said printed circuit
wiring boards; a second cover having a second intake port adapted
to supply air into the first intake ports through a second air
passage provided in the same direction as the direction of the
initial coolant air delivery, and a second exhaust port adapted to
discharge air exhausted from said first exhaust ports of said first
air passages in the same direction as that of the initial coolant
air delivery from the second intake port, said second cover
defining a third air passage in cooperation with the printed
circuit wiring boards to cover the first covers and the blowers and
a partition wall secured to the first covers and to the second
cover so as to separate air of the second intake port provided in
the second cover and the second exhaust port.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be described in more detail in
conjunction with the accompanying drawings, in which:
FIGS. 1A to 1D are a perspective view, front view, right-sectional
view and plan view of a first embodiment of the invention,
respectively;
FIGS. 2A to 2D are a perspective view, front view, right-sectional
view and plan view of a second embodiment of the invention,
respectively; and
FIG. 3 is a perspective view of one modification of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Throughout the respective drawings, unhatched or unshaded arrows
denote the direction of air flow passing through a duct which is
exclusively used for introducing air therein under suction, hatched
arrows indicate the direction of air flow passing through an air
passage defined by an inner duct 6', and shaded arrows indicate the
direction of warmed air flow passing through a duct which is
exclusively used for discharging air outside.
The structural features of the first embodiment of the invention
are shown in FIGS. 1A to 1D. A blower 4 is mounted on the opposite
side-portions of a support 3. An inner duct 6' covers
heat-generating electronic components 1, while an outer duct 6 is
divided into two sections by means of a partition wall 8 with one
of the sections serving as an exclusive-use intake duct 30 and the
other serving as an exclusive-use exhaust duct 31.
Air 20 is introduced as a coolant through an intake port 11 into
the intake duct 30. The intake duct 30, as shown in FIG. 1D, has a
bottom surface defining the intake port 11 as well as a top surface
defined by a seal plate 28 (FIG. 1B). An "L"-shaped space is
defined by the partition wall 8, the inner duct 6', and the outer
duct 6. Air passing through the inner duct 6' in the direction of a
hatched arrow cools the electric components 1 mounted on a printed
circuit wiring board 2. The air warmed by the heat produced from
the electric components 1 is delivered from the blower 4 into the
exhaust duct 31 as shown by shaded arrow 22. Since air in the duct
31 has been warmed, the air may be naturally discharged through the
exhaust port 10 in the direction of arrow 23.
The structural features of the second embodiment of the invention
are shown in FIGS. 2A to 2D. The partition wall 8 for separating
the intake side from the exhaust side of a double-walled duct is so
inclined that the cross sectional areas of the intake port 11 and
the exhaust port 10 may be both maximized.
Air 24 introduced as a coolant through the intake port 11 flows in
the direction of an arrow 25 from the blower 4 into an air passage
defined by the inner duct 6' in a manner similar to the first
embodiment. According to the second embodiment, the passage defined
by the exclusive-use intake duct 30 is progressively narrowed by
means of the inclined partition wall 8. Since the cross-sectional
area of the intake duct is constant as shown in FIGS. 1A and 1D in
the first embodiment, the coolant air 20 introduced under suction
is taken into respective blowers 4 in the course of the upward air
delivery, thus resulting in a decrease in air flow rate. As a
result, the velocity of air flow in the neighborhood of the blowers
lacks uniformity. In contrast thereto, according to the second
embodiment, the partition wall 8 is so inclined that the
cross-sectional area of the duct 30 is reduced in proportion to a
decrease in air flow rate in order to achieve a uniform air
velocity at the blowers.
Air delivered through the air passage defined by the inner duct 6'
and heated by heat produced from the electric component 1 is
discharged from the blowers 4 into the exclusive-use exhaust duct
31 in the direction of shaded arrow 26. Thereafter, the warmed air
26 is discharged through the exhaust port 10 outside in the
direction of arrow 27. In this respect, the cross-sectional area of
the passage defined by the duct 31 is progressively increased
upwards by means of the inclined partition wall 8 to accommodate
itself to the flow rate of the air 26.
In a modification of the invention, shown in FIG. 3, a thermally
conductive member 7 such as a heat pipe and the like is provided
with one end thereof contacting the heat-generating electronic
component 1 producing a large quantity of heat and with the other
end thereof projecting through a hole 32 provided in the inner duct
6' into the exclusive-use intake duct 30, that is, one of the
spaces partitioned by the partition wall 8. As a result, the
temperature of such an end of the conductive member 7, which
contacts the component 1 becomes higher than the temperature within
the duct 30 so that heat may be transferred from the component 1
through the member 7 into the intake duct 30. In other words, the
member 7 conducts heat from the component 1 into the duct 30. This
action takes place in cooperation with heat produced from the
component 1 with the aid of coolant air flowing through the inner
duct 6' of the double-walled construction. Therefore, the paths to
expel heat dissipated are increased in number as compared with the
construction free of the member 7. Accordingly, the temperature
difference dTc resulting from the thermal resistance prevailing
from ambient air surrounding the heat-generating electronic
component 1 to this component as shown in equation (1), may be
reduced so as to maintain the temperature of the component 1
relatively low. In this respect, though heat transmitted from the
component 1 through the conductive member 7 into the intake duct 30
raises the temperature of air in the intake duct 30, it can be
neglected, as compared with the total quantity of heat produced
from all the heat-generating components 1. Stated differently, a
part of heat produced from the component 1, which generates an
extremely large quantity of heat, may be dissipated throughout the
support 3, thus enhancing the cooling capability.
* * * * *